81 XJ550 Idle Issues

I'll start by saying this is my first post here but I have read many articles from this website over the past few weeks (thanks for the help you guys have already given.) My name is Jake, I'm from southern Ontario and although not licensed I work in the automotive industry by day and occupy my spare time with more car stuff at home. I would consider my mechanical knowledge of motorcycles to be "above average" but these particular machines have some technology that was probably brilliant years before my time. And lets face it, I'm not that old and thus not that experienced.

So here is the story. I only bought this bike a month ago. It had a slew of issues, some would have called it a basket case though it didn't cost me much. When I bought it, the seller boosted it (it had no battery) from his diesel truck, it ran fine on his truck after a little bit of starter fluid to get it going. Appeared to idle fine for him as it sat there running the whole time we were chatting. The next day I went out to do a proper assessment of what I had and what I needed to do. To be very brief; the left signals did not work, the right signals came on when the key was turned forward (and stayed lit, no blinky stuff), the headlight didn't work, it needed a battery, the back tire was balder than Howie Mandel, the front brake was stuck on (possibly from us taking it out of the sellers' truck), it had no air filters or a stock air box or anything at all really, the exhaust has been replaced? with a 4-into-1 header type exhaust with an empty exhaust tip that was probably designed for a pickup truck (someone welded a tab onto it so it would bolt up), the exhaust on the left side of the motor (choke side) has a broken bolt - possibly two, as I've noticed the other 3 are all studs with a nut, this has only one bolt going INTO the motor, and the choke and clutch cables were both replaced with what appears to me to be bicycle brake cables.

TL;DR: the bike was a mess when I got it. Since then, my starter died and I found a replacement, I've fixed the signals and headlight, replaced the clutch cable, rigged up a choke assembly on the carb itself (not using a cable but rather a lever on the choke handle where the cable used to be attached), replaced the battery, new rear tire, found a factory muffler that had been emptied but still has a baffle for SOME restriction, tore down the carbs and cleaned them to the best of my ability and using some advice from this site. (They were surprisingly clean before I touched them.) And lastly I just recently made an attempt to check/adjust the float height to a xjbikes-user-suggested 21.5mm from the gasket surface to the bottom-most part of the floats. They weren't far off from this either actually.

If I haven't lost you yet, here's my problem. The bike is hard to start when its cold. Starter fluid/ether will get it running though after a few seconds of trying but it will stall if I let go of the throttle. Regardless of engine temp. Once it warms up I can hear the exhaust leaking near the manifold stud that's missing, but it'll still run. The bike runs great and doesn't hunt through the rpms at all when I snap the throttle, and it revs up/down smoothly. But if at any point I let off the throttle it will stall within a second or two. When I choke it a little it will stay running but idle high when its cold, but as the engine warms up it will stall eventually with the choke on. I've tried many things suggested here so far and I'm not able to diagnose the issue myself. Any help would be appreciated and I already thank you if you've taken the time just to read this textwall.

I'd be happy to supply any other info you might need or try things out as you suggest them.

Editted just to say that I definitely intend to repair the broken stud on the exhaust manifold. It's looking like I'll have to drill it out and tap a new set of threads to bolt it back tight.

 

First thing you need to do is to make sure that the valve clearances are in spec. You will never get the carbs adjusted correctly until this has been done. Out of spec valve clearances will also make the bike difficult to start. You also need to get a stock airbox and filter on the bike. These bikes do not like open air systems or pods. Find the article on here called "church of clean", and follow it exactly for cleaning and adjusting the carbs. Do not take shortcuts or you will never get your bike running properly. Working on these bikes is not difficult. Just take your time and ask questions if you need help. Post up some pics of your bike. Good side views of each side of the bike and pics of the motor will help us see any issues you may not know to look for.

 

Thanks for the quick reply, I'll get some pictures up here shortly. Checking the valve clearance is not something I thought to do only because of how well the bike seemed to run once actually started. I will get out and check the valve clearances as soon as I can. As for the air filter, I have also read that they don't respond well to pod filters, but I haven't been able to locate a stock air box for a reasonable price. I'll keep looking, but shouldn't the bike be able to at least idle without filters on? I mean most adjustments to the carbs would be difficult to say the least with an air box and a gas tank on the bike.

 

Where are you in Ontario. I have parts and special tools to tune up these bikes.

 

He's in the the states not in Canada...

 

Ontario, CA is in the U.S. now?!

On to the issue at hand. Valve clearances are critical, and the most often overlooked maintenance item on motorcycles. I would hazard a guess that they have never been checked during the life of your machine. Once they are in spec you should wet-set the float levels (the dry set you did is only a close baseline, not the actual spec), and adjust your pilot screws to 2.5 turns out from lightly seated. A Gunson Colortune will be helpful, but you can use the lean drop method to get the idle mixtures set if you don't have a Colortune.

When you cleaned the carbs did you make sure that the enrichment jets in the carb bowls were clean?

 

Sorry sometimes my brain doesn't work. But yes there is a Ontario in California.

 

I've updated my location to prevent further confusion.

The pilot jets were the only ones that weren't spotless. I let all the carb internals soak in carb cleaner overnight and blew them in the morning with compressed air. I did also set the pilot screws to 2.5 turns from base. That was one of the first things I tried. I'll be adding some photos and a very poor quality video of the bike "running" if any of these will help.



I extremely apologize for how bad the video is, but I think it gets the point across.


Edit: The carb boots in the pictures look a lot worse than they actually are. They show some age but the pictures make them look pretty bad. It doesn't seem that they're leaking with the old "spray wd40/carb cleaner at it while running" trick.

 

The video permissions are set to private.
By all carb internals do you mean only the metal parts, and not the carb body itself?

 

Apologies on the video permissions, should be fixed now. And correct, I used an aerosol carb cleaner on the carbs themselves and let all the jets soak in dishes of carb cleaner.

 

Your throttle shaft seals look like they have been leaking. Check the for sale section on here for an airbox. Post a wanted ad and maybe someone has one they will sell you. Lots of us have extra parts. Without the airbox you won't get a proper tune. Also, check the manifolds for cracking. That will also cause problems. Don't let all of this discourage you. You will get it running right.

 

+1 on throttle shaft seals. Those stains are a huge telltale that yours are toast.

 

Pm'd a member with 550 Maxim parts bike on the airbox, thanks for the advice zombiehouse. Also, I did notice the stains around the end of the throttle shaft, I guess I overlooked it seeing as the stains start near the top of the carb. I had assumed someone had just left a leaky fuel line on it for too long or something.

I'm beginning to accept that this isn't likely going to be a bike I'll be riding this year, against my best wishes. I was hoping this bike would be a quick fix. My last bike (1977 Suzuki GS750) was in far worse condition to start but the bike just seemed to have more desire to live again lol.

 

Hey Jake don't get discouraged.
I'm in Ontario as well and just got an 82 xj550 and with the help of everyone on this forum it's almost road worthy.
It's my first bike and I'm learning a lot.
Good luck to you!
-EM

 

Good to hear, EarMachine. I have no doubts it will get there. But when it fired up on the day I bought it, I had better hopes for how far I'd be almost a month later.

 

Just keep thinking of where you will be when you're all done. Old bikes are worth the effort spent.

 

Jake, do not despair. These guys know what they speak of. Keep asking questions as you move through it. Take the carbs off again and go to Church, spend some more $$ for proper rebuild kits and you will have the coolest bike on the block!

 

Thanks for all the help. I'm working with another member on here to get ahold of an airbox, a proper choke assembly and new carb boots. In the meantime I'll check and adjust the valve clearance as well as do an oil change and get some brand new plugs in there. Hopefully I can fix the exhaust manifold stud that broke as well.

Will post an update when I know more.

 

I have a question about this. The "choke" is really an enrichemnt circuit and is a part of each carb. There is an enrichment plunger linkage that is external to each carb, but that is a part of the carb rack, and a control lever on the left switchgear that conects the cable that makes the whole system work. What part are you missing?

 

I'm missing the cable and both ends. The cable that the previous owner had on it was clearly not the correct cable. It only moved the linkage on the carb about a quarter of the full range of motion it can go. I removed it entirely. I have only the handle that fastens to the handgrip assembly with the signal light switch etc. Nothing that properly fits on the carb end of the choke cable. Until now any time I've said that I've applied the choke I've been physically holding the choke lever off the carb to a certain spot. All the way, half way, etc.

Jake

 

Just a quick update. Ok maybe not so quick. Lol. As for the stains on the carb at the end of the throttle slide, I think that was just a funky picture turnout. It's not that stained in actuality. Plus I cleaned it really well when I first tore the carbs down and I haven't noticed anything since.

I did get out to check the valve clearances and I have interesting results.
Cyl #1 Ex: <0.0015" In: <0.0015" ***
Cyl #2 Ex: 0.004". In: 0.004"
Cyl #3 Ex: 0.006". In: 0.004"
Cyl #4 Ex: 0.004". In: 0.004"

*** 0.0015" is as small as my feelers go. Cylinder 1 is the one that has a broken exhaust manifold stud. I've removed the exhaust but I don't have a small enough tap to rethread for a new bolt, going to borrow a friends tomorrow. I also need a new manifold gasket for this spot as the old one is dead. I'm guessing this cylinder was running extremely hot. Compression is still as good across the board as it was when I got it.

Should be able to go get a shim set on thursday. I should also have the exhaust fixed by then and we will see where we are at by the weekend.

Jake

 

valve specs from FSM (factory service manual the .006" bothers me as an overlapping spec. have you checked your current shim sizes? are you buying a factory shim set or just the ones you need?

 

I'm told I can buy a set of assorted shims at my local Yamaha dealer and use what I need. This way I can pull them out, use the chart to determine what they should be, and replace right away. Rather than pulling them all and waiting for replacements. And having to go through the motions twice.

Jake

 

those kits are not cheap. and will have many you will not use, you can sell extras. oem shims run about 27$ each after market around 9$ after market kits do not have the full range of shims 245 is not available from some aftermarket kits

 

Jake, we love you here but for cripes sake you need to listen to the advice. Don't make excuses.

I am not sure if WD-40 is as effective as propane/ starting fluid.
If your throttle shaft seals have not been replaced, chances are good that they are 34 years old - they need to be replaced.

Don't be lazy with your work on these fine old machines. Measure all of your clearances, remove each shim (one at a time) verify the stamped size is accurate and document the shim size with clearance measurement. Do some math, see if you can do the shim dosey-doh, talk with Dave about swapping shims from his pool (will cost you postage and a few days). Or contact XJ4Ever; or try and see if a local place has spare shims and are willing to swap.

Don't just 'go by the chart' re-measure after replacing the shims; rotate the engine and re-measure again - if you don't have the same measurement, then ask why? And measure again. . . .

Whatever you do; do NOT take short cuts and do NOT ignore advice given. These guys have been down the road of bringing the beast back to life and they know what they are talking about.

 

Stumplifter, I'm pretty confused about where I ignored someone's advice. If anything I can't stress enough how much I appreciate the time you guys have put in to help me out. I haven't ignored anyone's suggestions and I'm working my way through checking everything suggested. Should I replace the throttle shaft seals because of their age? Probably. All I was saying is that the first photo I posted of the left side carb looked way worse than it actually looks in reality. I intend to replace it when I tear the carbs back down. However for the meantime I'm starting with the valve clearances as recommended.

As for the valve shims, all I had time to do last night was actually measure the clearances that I have. I don't have a shim removal tool and I'm uncertain about the wire/ziptie method. My local Yamaha dealer claims to have all of the different sizes of shims for this bike. I just need to bring in my valve clearance measurements and my old shims and they will sell me the appropriate shims. They quoted about $4.00/shim. When I said kit I meant an assortment of valve shims and I would have to only use what I need. I didn't mean a replacement set of factory (the wrong size) shims.

Again I apologize if at any time I mistook someone's advice or seemed unappreciative. I can't express enough how much you guys have helped, even though you've probably all been through this exact same scenario a hundred times.

Jake

 

The thing is, you can't bring in the old shims all at once. If you turn the engine without a shim in every bucket you will damage the buckets, so to remove all of them at once requires removal of the cams.
The zip-ty (or insualted copper wire) method works. If you are unclear as how to do it, I can write it up for you.

 

Would it be smartest then for me to pull a shim, document size, place it back, and repeat across all valves? Then just bring the last shim to my dealer for diameter reference?

Jake

 

Yes, that is SOP. You don't have to have a shim with you (but it won't hurt to) just make sure you get 29mm diameter shims and not 29.5mm. Also don't get any with a chamfer on one face/edge. Our buckets need flat shim faces.

 

Good to know, thanks again for the info. Will likely post again tomorrow evening with where I'm at.

Jake

 

Jake my local Yamaha shop told me they had plenty of shims in stock also. BUT when you get there they are 29.5mm instead of the 29mm that these bikes use. Make sure you do not try to put the 29.5mm shims in there, yes they look the same but there not. I think some of the new bikes have went back to 29mm shins but NONE, thats 5 total in the DFW area had the correct size shims, ended up having to get mine on Ebay, didnt know about the shim pool at the time. If they are 4 bucks locally I am betting they are the wrong size shims for these bikes. Just a heads up

 

I appreciate the heads up Team43 and k-moe. I'll bring my calipers with me when I go to the shop in the morn. I'll need 4 replacement shims. In/Ex for Cyl 1, then just Exhaust shims for cyl 2 and 4. I have two local places I intend to check tomorrow in the morning. I'll get back on here later tomorrow with an update.

Jake

 

there is a chart in the diy forums that will tell you the shims size you will need after you read the size. read this link
http://xjbikes.com/forums/threads/airhead-valve-adjustment-with-pics.14827/

 

So just to keep you guys updated. My morning today went pretty well flawlessly. I found 2 of the 4 shims I needed at my local dealer and the other 2 at a local guys' shop. I went home, swapped the shims out, rotated the motor a few times to make sure they were all seated properly, and then rechecked clearances. All of my valve clearances are within spec now. I also drilled and tapped new threads on my exhaust manifold where the one stud had been damaged. Because I couldn't help myself I threw the exhaust (with new gaskets), carbs and tank back on and started the bike. It doesn't appear to be leaking exhaust any more and it both runs and idles better but still doesn't idle on its own below 2000 rpms.

Next step for me is to find an airbox, carb boots, and to start over on the carbs.

Jake

 

Glad to hear it's going well! Just be patient and don't do anything you aren't sure of!
-EM

 

Ok so this project has taken a giant downhill turn. I had the carbs apart over the last couple of days to do some more cleaning. Over the course of these couple days (and I don't know whether it was from carb cleaner fumes in my garage, or the extreme humidity we've had but) my vacuum piston diaphragms have all gotten extremely misshapen and warped. They do not even kindof fit anymore. They feel way too big. I've got them sitting in a cool, dry, dark area trying to see if they'll stiffen up a bit. But I'm not hopeful. I called around to find new ones and they're nearly $1000 CAD for the set. Mikuni sells aftermarket ones and they're still $150 each. Way more than I intend to spend at this time.

Currently considering parting/selling the bike but I'm open to hear your thoughts.

Jake

 

Got the diaphragms to fit. Waiting on throttle shaft seals and new o-rings for the float seats.

Jake

 

Carb cleaner is the enemy of rubber parts. You're lucky that the diaphrams were in good shape before they got exposed to it. Even Viton will swell when exposed ot carb cleaner, and as you saw some parts return to their normal size after a few hours of sitting in the air, but others don't (throttle shaft seals for example).

 

I don't think I ever sprayed carb cleaner on them directly, just onto a rag to wipe the slides clean. Though they sat on my workbench about 5 feet from where the rest of the stuff was soaking. And my garage isn't very well ventilated. I was pretty shocked to see the condition they were in this morning. The material was sticky and had stretched so much it was bigger than the top "cap" of the carb. Swelled to be at least half an inch bigger in diameter. I thought for sure that they were going to be junk.

Though I did learn my lesson with carb cleaner + rubber when cleaning the float needle seats. The o-rings fell apart with just a bit of carb cleaner on a rag.

Jake

 

Stumbled across this site a few times (for replaecement diaphragms) http://jbmindustries.com/Dimensions.htmll but no first hand experience - prices look good though